Current regulating device



May 5, 1931 D. R. DE TAR CURRENT REGULATING DEVICE Filed July 20, 1,928

Inverfl'or' Donald R 5 6/ DeTcm,

H55 ATToFneH.

Patented May 5, 1931 UNITED STATES DONALD R. DE TAR,

PATENT OFFICE OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMIPANY, A CORPORATION OF NEW YORK CURRENT REGULATING DEVICE Application filed July 20,

My invention relates to current regulating devices, more particularly to variable rheostats and potentiometers such for example as used in radio apparatus, and has for its general object the provision of an improved construction for devices of this character.

More specifically, the present invention provides an improved arrangement whereby the various parts of a current regulating device of the above character may be readily assembled and held in operating relation together with an improved form of movable spring contact arm for enabling good contact to be maintained throughout a long period of service, as well as other advantageous features of construction pointed out more fully hereinafter.

For a more complete understanding of my invention reference may be had to the accompanying drawings in which Fig. 1 is a rear elevation of a rheostat embodying my invention; Fig. 2 is a side elevation in section taken along the line 22 of Fig. 1 looking in the direction of the arrows; Fig. 3 is a perspective view showing the parts of the device in detached, unassembled relation; and Fig. 4 is a view of a contact arm showing a modification thereof.

Referring to the drawings, in carrying out.

my invention in one form I have provided a rheostat comprising a base member 10, on which is secured a high resistance element 11 and a low resistance element 12. These ele- .ments are arranged to provide a varying resistance er linear unit whereby a tapered or non-uni orm current control may be obtained as described and claimed in the copending application Serial No. 294,251 of William L. Bond, filed July 20, 1928, assigned to the same assignee as this invention. It is preferred that the base member 10 be made of porcelain although any other suitable insulating material may be used. An operating shaft 13 passes through the base member 10 at approximately the center thereof, and to one end of the shaft 13 is attached a movable contact arm 14. Contact terminals 15, 16 and 17 are provided, being connected respectively to the ends of the high resistance element 11 and the contact arm 14. The base 1928. Serial No. 294,277.

member 10 is preferably formed in one piece and is provided with apertures 18 through which suitable bolts, not shown, may pass in order to secure the rheostat to a panel or instrument board] The operating shaft 13 passes through and is rotatably mounted in a headed metallic bushing 19, held in place in an aperture 20 by a nut 21. The shaft 13 is prevented from longitudinal movement through the bushing by a split rin 22 in engagement with the bushing 19. (fine end of the shaft 13contains a central indentation and a transverse slot 23 and as shown more clearly in Fig. 3, the partially cut-away hub portion 24 of the contact arm 14 is provided with an aperture 24 of a size and shape such that the hub of the contact arm may be pushed overthe end of the shaft 13 with the parts of the hub around the aperture in locked-engagement with the slot 23. After assembling, the end of the shaft is peened over, thus holding the hub of the contact arm 14 securely in non-rotating engagement with the end of the operating shaft. The partially cut-awayhub portion 24 of the contact arm 14 has integral therewith small projections 25 and by the engaging of these projections with the enlarged end of the terminal 17, as shown in Fig. 2, an eflicient wiping contact is obtained. The terminal 17 is secured to the base by means of a rivet 26. Moreover, by partially cutting away the hub portion 24 of the contact arm 14, as illustrated in Figs. 1 and 3, an increased resiliency is obtained in the contact arm, thereby insuring a more efficient wiping contact with the resistance element.

The base member 10 is substantially circular in form and contains an indentation or groove 28 of predetermined length in its cylindrical periphery extending, as shown, around approximately one-third of the periphery. .The groove 28 is of the proper shape and size to hold the low resistance element 12. V A I The high resistance element 11 comprises an insulating strip or core 29 about which is wound a high resistance conductor 30. The high resistance element is ofsubstantially circular shape and of a width slightly greater than the width of the periphery of the base 10. The low resistance element 12 comprises an insulating strip 31 about which is suitable insulating material. While I have edge shown the low resistance conductor 32 'as being made of a wire larger than the wire forming the high resistance winding 30, I do not wish to be limited to this particular arrangement since the resistance element may take other forms. For instance, the resistance element 12 might be wound with the same size or even smaller wire than the resistance'element 11, depending on the effective resistance desired. The high resistance element 11 may be wound either with bare wire or with insulated wire. If insulated wire is used the inside and the exposed of the element 11 should be cleaned of the insulation. The low resistance element 12 is preferably wound with bare wire.

The metallic terminals 15 and 16 are l.- shaped'and one end of each terminal is cut as shown in F ig. 3, forming two projections 33 and 34. The projection 33 contains a small hole into which the end of the high reslstance conductor 30 is placed and preferably soldered. Stop members 36 integral with the terminal'l'? act to stop or limit the angular movement of the contact arm 14.

One end of the terminal 17 is enlarged and contains an aperture 37 through which the shaft 13 passes, the enlarged end of the terminal serving as a bearing for the projections 25 on the contact arm, as described hereinbefore. The outer ends of the terminals 15, 16 and 17 are cut and bent as shown in Fig. 3 to facilitate the soldering thereto of external connections.

In order to secure the vaiious parts of my device in position, a contractable metallic clamping member 38, substantially circular in shape except for the end extensions 39 and 40, is provided for surrounding the base 10 with the resistance elements 11 and 12 interposed between the base and the clamping member. The extensions 39 and 40 contain apertures through which a bolt 41 is placed and by screwing this bolt into a nut 42 the end extensions 39 and 40 are drawn together to contract the clamping member 38 around the high resistance element 11, thus holding the low resistance element 12in the groove 28 between the high resistance element 11 and the base 10. A flexible insulating strip 43 of approximately the same width as the clamping member 38 is adapted to be placed between the clamping member 38 and the high resistance element 11.

In Fig. 4, I have shown a slightly difi'erent form of contact arm. The contact arm 45 is formed of spring metal such as phosphor bronze with a. cut-away hub portion 45' similar to that described in connection with Fig.

However, the portion of the modified contact arm 45 extending away from the hub portion 45 is divided into two contact fingers 46 and 47 the contact-making ends 48 and 49 of the fingers being trough shaped in order to secure a good sliding contact with the edge of the resistance element. It can be seen that in case one of the finger ends 48 or 49 should rest on a dead spot, that is, a spot where the insulation of the resistance conductor has not been completely removed, the remaining finger end, will still form a contact with the conductor. By thus dividing the contact arm longitudinally a smoother sliding action is obtained with a resulting lessening of noise and vibration.

In assemblingmy rheostat the low resist,-

ance element 12 is placed in the groove 28 of the base 10, after which the high resistance element 11 is placed around the periphery of the base member thus holdin the low resistance element 12 in place. e terminals 15 and 16 will be clamped between the high re- It will be observed that the winding 32 of the low resistance element 12 is held, throughout the length of the low reslstance element, in parallel, electr1cally contactmg relation with the inside of approximately one-third of the winding 30 forming the high resistance element 11, the bare surfaces of the two windings being pressed against eachother'due to the clampm action of the ring 38. The groove 28 is o a width such I that, when the resistance elements are in position, the outer edge of element 12 W111 be spaced inwardly from the contact-mak ng edge of the element 11, that is, the low resistance element 12 will not be engaged by the contact arm 14 as this arm moves over and in contact with the high resistance eleinent 11.

Assuming that the contact arm 14 1s moved from starting position at a uniform rate in a counter-clockwise direction, as viewing Fig. 1, the efi'ectiveresistance between term nal 16 and terminal 17 will increase uniformly at a certain rate until the end of the contact arm passes the point at which the upper end of the'low resistance element 12 engages the high resistance element 11. From this point the resistance will also 1nis due to the fact that'the two resistance ele- 4 ments are in parallel throughout the length alone.

While I have shown my current regulating device with terminals at each end of the resistance so that the device may be used as a potentiometer, the device mayobviously be used as a rheostat by making connections only to the terminals 16 and 17.

While I have described my invention as embodied in concrete form and operating in a specific manner in accordance with the provisions of the patent statutes, it should be understood that I do not limit my invention thereto, since various modifications thereof will suggest themselves to those skilled in the art without departing from the spirit of my invention, the scope of which is set forth in the annexed claims.

What I claim as new and desire to secure by Letters Patent of the United States, is

l. Ina current regulating device, a base, a resistance element disposed around the periphery thereof, contractable clamping means surrounding said base with said resistance element interposed between the base and the clamping means, and means for con-- tracting said clamping means to secure said resistance element in position on the periphery of said base.

2. In a current regulating device, a base having a substantially cylindrical periphery, a resistance element disposed around the periphery of the base, a contractablev clampin strip surrounding the resistance element, and means for drawing the ends of the strip together to contract said strip and thereby secure said resistance element in position on 'means, and means for contracting the clampthe periphery of said base.

3. In a variable resistance device, a base, a plurality of resistance elements disposed in overlapping relation on the periphery of the base, contractable clamping means surrounding the base with the overlapping resistance elements interposed between the base and the clamping means, and means for contracting said clamping means to secure said resistance elements to said base in adjacent electrical parallel contacting relation.

4. In a variable resistance device, a circular base, a wire wound resistance element disposed on the periphery thereof, terminals loosely-connected with said resistance element, contractable clampmg means surrounding the base with the resistance element and said terminals interposed between the periphery of the base and the clamping ing means to secure said resistance element and said termlnals 1n fixed posltlon on the periphery of sa1d base.

5. In a variable resistance device, a base having a substantially cylindrical periphery and a pair of spaced apart grooves formed therein, an annular wire wound resistance element disposed around the periphery of said base, terminals loosely connected with the end turns of said resistance element, and

a contractable clamping ring for encircling and securing the said resistance element in. position on the periphery of said base with said terminals held in said grooves betweensaid resistance element and said base by the clamping action of said ring.

' 6. In a variable resistance device, a base having a substantially cylindrical periphery provided with a grooveextending around a portion thereof, a substantially annular wire wound resistance element disposed around the periphery of said base, an arc shaped resistance element in said groove, and a contractable clamping ring for encircling and securing said annular resistance element around the periphery of said base with said are shaped resistance element held throughout its length in said groove in contacting relation with the inner side of a portion of said substantially annular resistance element.

7. In a variable resistance device, an annular resistance element, a rotatable shaft mounted at substantially the axis of said resistance element and provided with a longitudinal slot therein at one end thereof, and a movable contact arm for making contact with said resistance element, said contact 8. In a variable resistance device, an annular resistance, a shaft rotatably mounted at substantially the axis of said ,resistance element and provided with a longitudinal slot therein at one end thereof, a movable contact arm for making contact with said resistance, said contact arm being provided at its hub with fingers engaging in said slot to prevent relative rotation between said shaft and said contact arm and having a partially cut-away hub portion, the portion of said arm extending from sa1d hub portion being divided lon gitudinally into a plurality of contact making fingers, engagement with the fingers of the hub portion of said contact arm and having stops formed integrally therewith for limiting the rotary movement of said contact arm.

9. In a variable resistance device, an insulating base, a pair of resistance elements mounted on said base, a clamping means for securing said pair of. resistance elements to said base in parallel electrical contacting relation, a movable contact arm for making contact with one of said elements, the other a'stationary conductor in sliding of said elements being mounted in spaced relation to said contact arm.

. 10. In a variable resistance device, an insulating base havinga substantially circular periphery, an annular resistance element, an arc-shaped resistance element, a groove in the periphery of said base for receiving said arc-shaped resistance element, a clamping ring for encircling and holding said annular resistance element around said periphery and in contact with said arc-shaped resistance element, and a movable contact arm cooperating with said annular resistance element, said arc-shaped resistance element being held in said groove in non-engaging relation with said contact arm.

In Witness whereof, I have hereunto set my hand this 19th day of July, 1928.

DONALD RUDE TAR. 

